Diagnosis of Plant Disease and Nematode Problems

Correct diagnosis is the first step in controlling a condition caused by disease organisms or nematodes. Since fungi, bacteria, nematodes, mycoplasma and viruses are microscopic in size, it is necessary to follow certain procedures to insure proper identification. The following series of steps will aid in taking a more direct approach.

  • Carefully observe all symptoms associated with a condition. Formulate a description in your mind or on paper and check to see if the statement is true without exception.
  • Compare plants to see if they are similarly affected in all parts of the field or yard.
  • See if non-related plants are similarly affected. Most disease-causing organisms are host specific and do not affect a large number of plant types. If a similar leaf spot or burn is observed on different plant types, then one might expect a drift of toxic substances. On the other hand, certain diseases like cotton root rot might affect a number of plants, but you could rule out corn or other grasses, which are not susceptible.
  • Get as much information as possible to help diagnose the problem. County Extension agents have a number of publications that will be helpful.
  • If it is not possible to correctly identify the problem at this point, one should select a representative specimen for observation by the county Extension agent.
  • Microscopic examination may be required. If this is the case, a specimen can be mailed to the Texas Plant Disease Diagnostic Laboratory (Submission forms and fees schedule can be found at the plant clinic forms page). There is a $35.00 minimum fee for each sample. Forms are available online or from your AgriLife Extension county office. ┬áPage 2 of form contains information on how to collect, package, and mail specimens.
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